Power and free conveyor

ABSTRACT

A conveyor of the power and free type having a power track for a propelling member spaced above a carrier supporting track. Each carrier is provided at the front end with a rigid main driving dog and at the rear end with a rid combination releasing cam and auxiliary driving dog. Forwarding motion is imparted to a carried by a pusher unit on the propelling member, the pusher unit including an auxiliary driving face and a movable pusher member having main driving and holdback faces. At a normal spacing between the power and carrier tracks, the main driving and holdback faces on the pusher member are engageable with the main driving dog of a carrier and the pusher member is movable to a nondriving position in response to engagement with a stop or with the auxiliary driving dog of a preceding carrier. At a reduced track spacing, the pusher member is movable to a position of positive driving engagement with the main carrier driving dog, or alternately, the auxiliary driving face of the pusher unit is engageable with the auxiliary driving dog of a carrier.

United States Patent [72] Inventor George D. Lempio Detroit, Mich.

[2]] Appl. No. 811,469

[22] Filed Mar. 28, 1969 [45] Patented Feb. 2, 1971 [73] Assignee Jervis B. Webb Company a corporation of Michigan [54] rows: AND FREE CONVEYOR Primary ExaminerArthur L. La Point Assistant Examiner-Robert W. Saifer Attorney-Farley, Forster 8: Farley ABSTRACT: A conveyor of the power and free type having a power track for a propelling member spaced above a carrier supporting track. Each carrier is provided at the front end with a rigid main driving dog and at the rear end with a rigid combination releasing cam and auxiliary driving dog. Forwarding motion is imparted to a carrier by a pusher unit on 18 7 D" the propelling member, the pusher unit including an auxiliary mg gs. driving face and a movable pusher member having main driv- [52] US. Cl 104/172 ihg and holdback f At a normal Spacing between the 1 3'- 8 17/"2 power and carrier tracks, the main driving and holdback faces [50] Field of Search 104/172, on the pusher membelate engageable with the main driving 173 dog of a carrier and the pusher member is movable to a nondriving position in response to engagement with a stop or with [56] Reennms Cited the auxiliary driving dog of a preceding carrier. At a reduced UNITED STATES PATENTS track spacing, the pusher member is movable to a position of 3,074,355 1/1963 Schreyer I04/ 1 72 positive driving engagement with the main carrier driving dog, 3,418,949 12/1968 Fromme etal l04/l72 or alternately, the auxiliary driving face of the pusher unit is 3,503,337 5/ I970 Haase. engageable with the auxiliary driving dog of a carrier.

PATENITEUFEBZ I9?! 3559585 sum 1 or 4 m J R m 4r mi W1 l JM 4 6 i 0 z 6 m I. I. i v 3Y1 mu 3 W L3 w i: wk Q z @5 9 6% 1 r M 4% I I mwm mm R N o .h- NW ATTORNEYS POWER AND FREE CONVEYOR BACKGROUND OF THE INVENTION l Field of the Invention This invention relates to improvements in power and free conveyors of the type in which carriers may be releasably propelled for stopping and accumulation, positively propelled, and transferred between power lines.

2. Description of the Prior Art A conventional power and free conveyor includes a tracksupported endless propelling member with pushers thereon, hereinafter referred to as the power line, mounted adjacent to a track on which carriers are supported, each carrier having a driving dog projecting toward the power line and engageable by a pusher thereof. Conveyor systems of this type may have a network of carrier tracks and a plurality of power lines with requirements for the transfer of carriers between power lines, the stopping and accumulation of carriers along a power line, and the propulsion of carriers along vertical curves with a positive connection between a pusher and a carrier.

Two types of construction have been used or proposed to satisfy the requirement for the stopping and accumulation of carriers. In one of these types, the carrier is provided with a driving dog which is movable between driving and nondriving positions relative to a pusher, as shown in U.S. Pat. No. 3,044,416. The second type of construction employs a pusher which is movable between such positions relative to a carrier driving dog either by a cam on the power line as shown in U.S.

'Pat. No. 3,099,228 or by a cam on the carrier as found in German Pat. No. l,l43,499 and U.S. Pats. Nos. 3,418,948 and 3,418,949.

The present invention answers a need for a simple, inexpensive conveyor construction of the movable pusher type which will not only permit the stopping and accumulation of carriers but which will also meet the other conveyor system requirements for the positive propulsion of carriers and the transfer of carriers between power lines.

SUMMARY OF THE INVENTION The invention provides new combinations of elements on the propelling member and carriers of a power and free conveyor which function in different ways at varying spacings between the power and carrier tracks to satisfy the requirements mentioned above. On the propelling member these elements are formed on longitudinally spaced pusher units, each having an auxiliary driving face and a pusher member provided with main driving and holdback faces, the pusher member being mounted for limited movement relative to the propelling member between retracted and extended positions and being gravity biased to the latter position. The auxiliary driving face is formed on a portion of the pusher unit which is forwardly of the main driving and holdback faces on the pusher member and which is closer to the propelling member than are the main driving and holdback faces when the pusher member is in its extended position.

On each carrier the elements are found on relatively fixed members projecting toward the power track at the front and rear ends of the carrier. The front member includes a main driving dog, a main holdback dog, a secondary holdback dog located forwardly of the main holdback dog and projecting a lesser distance toward the power track, and a guide surface between the two holdback dogs. The rear member includes an auxiliary driving dog and a pusher-retaining cam, the retaining cam having a transverse dimension less than that of the main driving and main holdback dogs.

At a normal spacing between the power and carrier tracks, the main driving face of the pusher member is engageable with the main carrier driving dog and disengageable therefrom in response to contact of the holdback portion of the pusher member with a stopping device or with the auxiliary driving dog of a leading carrier. The holdback portion of the pusher has a camming action to produce this disengaging pusher movement, and the pusher-retaining cam on a carrier prevents reengagement of the auxiliary driving dog by the main driving face of the pusher. Thus a carrier can be stopped, and any following carrier which overtakes a stopped carrier will also stop and accumulate. In this stopping and accumulation of carriers, the main holdback dog serves as an abutment engaged by the stopping device or by the auxiliary driving dog of a leading carrler.

At a decreased spacing between the power and carrier tracks, the auxiliary driving dog of a carrier is engageable by the auxiliary driving face of a pusher unit to advance the carrier through a transfer zone.

Also at a decreased track spacing, a pusher member which is in engagement with a main carrier driving dog is moved thereby toward the retracted pusher position, and the secondary holdback dog of the carrier is moved into overlapping relation with the holdback face of the pusher member. This places the pusher member in nonreleasable engagement with the carrier, reduces the extent of relative longitudinal movement possible between the carrier and the pusher member, and results in positive carrier propulsion.

Other features and advantages of the invention will appear from the description to follow of the embodiments disclosed in the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a portion of a power and free conveyor of the invention, illustrating the propulsion, stopping and accumulation of carriers;

FIG. 2 is a sectional elevation, showing a stop, taken as indicated by the line 2-2 of FIG. 3;

FIG. 3 is a plan view, partly in section, of the construction of FIG. 2;

FIG. 4 is a side elevation showing the positive propulsion of a carrier at a reduced spacing between the power and carrier tracks; I

FIG. 5 is a side elevation similar to FIG. 4 but illustrating the propulsion of a carrier by engagement of an auxiliary pusher with a supplementary carrier driving dog; and,

FIGS. 6 and 7 are fragmentary side elevations showing the carrier propelling and accumulating action and an alternate form of pusher unit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1, 2 and 6, the power line consists of a track 10, of the enclosed type, supporting a propelling member 12 which is formed of alternate pairs of links 13 carrying a pair of supporting wheels 14 on a horizontal axis 15, and pairs of links 16 carrying a guide wheel 17 on a vertical axis 18, the links 13 and 16 being connected by pins 19. The supporting wheels 14 engage the lower flanges 20 of the track 10. Pusher units 22 (FIGS. 1, 4 & 5) are connected to the propelling member 12 at desired intervals, and the propelling member 12 is driven in the direction of the arrow 21 by a conventional drive unit (not shown).

Each pusher unit 22 is composed of a bracket 23 secured to the lower one of a pair of the links 16, and a pusher member 24 mounted on a pivot pin 25 carried by the bracket 23. The bracket 23 is a platelike member having a mounting pad 26 conforming to a portion of the surface of the link 16 and formed by laterally extending flanges, a rearwardly projecting tongue 27, and an enlarged portion 28 extending forwardly of the pusher member 24 and forming an auxiliary driving face. The pusher member 24 has a pair of side portions 30 forming a clevis end which straddles the bracket 23 and receives the pivot pin 25, the side portions being joined by a transverse web 31 underlying the bracket and by an upper web 32 overlying the bracket tongue 27. The pusher member is free to pivot about the axis of the pin 25 and is thus mounted for limited movement relative to the propelling member 12 between the retracted position illustrated in FIG. 4 and the extended position of FIG. 5, being biased to the latter position by gravity.

A main driving face 34 and a holdback face 35 are formed on the pusher member 24. the main driving face being located farther from the pivot pin than is the holdback face 35. and being inclined forwardly rather than extending in tangential relation to the axis of the pivot pin. The portions of the pusher member on which the driving face 34 and holdback face 35 are formed are transversely wider than the clevis portion 30, as shown in FIG. 2 and each of these driving and holdback portions have beveled side edges 37. The outer transverse surface of the web 36 on the holdback portion extends at an acute angle to the longitudinal centerline of the propelling member when the pusher member 24 is in extended position so as to provide a camming action urging the pusher member to retracted position in the event of contact of the holdback portion with an object in its path of travel.

Below the power track 10 are a pair of transversely spaced channel section track members 39 and 40 which form a carrier track suitably supported from the power track 10. Only the carrier track member 40 is shown in FIG. I in order to more clearly illustrate the construction of a carrier 42. This carrier 42 is of the multiple trolley type, having a front trolley 44 and a rear trolley 45 connected by a load bar 46, the trolleys being similar but not identical in construction.

Each of the trolleys 44 and 45 (FIGS. 1 and 2) has pairs of front and rear wheels 47, each pair of wheels being mounted on an axle 48 which extends through apertures in a pair of plates 49 and in a body member 50 mounted between the platesas shown in FIG. 2. Guide rollers 52 are mounted on the plates which are transversely spaced at their lower portion to receive a connector 53 which is secured between the plates on a pivot 54 and which pivotally suspends a load bar-supporting bracket 55.

The trolley body member 50 may take one of three forms. On the front trolley 44, (FIGS. 6 and 7) the body member 50 includes a portion 56 projecting upwardly towards the power track 10 and having a main driving dog 58, a main holdback dog 59, a horizontal guide surface 60, and a secondary holdback dog 61. As shown in FIGS. 2 and 3, the upper extremity of the portion 56 is enlarged transversely and formed with downwardly beveled sides 57. On the rear trolley 45, the body member 50 includes an upwardly projecting portion 62 which includes a retaining cam 63, a supplementary driving dog 64, a guiding bevel 65 and a forward plow 66, best shown in FIG. 3. The third fonn of the body member 50 is a combination of the first and second fonns described, including both the upwardly projecting portion 56 of the front trolley 44 and the upwardly projecting portion 62 of the rear trolley 45; and this third form is used for single trolley carriers or for the front trolley of multiple trolley carriers in installations where carriers are at some places transferred from in-line travel on a single track, as shown, to side-by-side travel on a pair of parallel tracks.

An alternate construction of a pusher unit appears in FIGS. 6 and 7, this unit also consisting of a bracket 70 and a pusher member 71 mounted on a pivot 72. The bracket 70 is formed by a pair of parallel plates secured to a line, 16 of the propelling member, the plates being joined by the pivot 72 and by a stop pin 73. The pusher member 71 is mounted between the bracket plates and has a driving face 74, a holdback face 75, a recess 76 receiving the stop pin 73, and a front end 78 which projects forwardly of the pivot 72, at least as far as does the part of the bracket around the pivot, and forms an auxiliary driving face.

The foregoing components, together with changes in spacing between the power and carrier tracks, coact to provide all types of carrier movement and propulsion which may be required in a power and free system, namely, the stopping and accumulation of carriers, the transfer of carriers under power, and the positive propelling of carriers.

Stopping and accumulation of carriers are illustrated in FIGS. 1, 2, 3, 6 and 7, and for this mode of operation, the power and carrier tracks are mounted at a normal spacing as indicated by the dimension 80. At this track spacing, and with a pusher member 24 or 71 in the extended position to which it is biased by gravity, the main driving dog 58 of the carrier is engageable by the main driving face 34 or 74 of a pusher member. and the holdback dog 59 of the carrier is overlapped by the holdback face 35 or 75 of the pusher member, although the extent of overlap is less than that between the pusher member and driving dog. The holdback or cumming portion 36 of the pusher member also extends into an interference position relative to the main driving dog 58, the auxiliary driving dog 64 and the retaining cam 63.

The pivotal mounting of the pusher member permits movement thereof between this engaged position relative to the carrier dn'ving dog 58 and a disengaged position relative thereto as shown in FIGS. 2 and 7, such movement resulting from contact between the holdback portion of a pusher member and a carrier stop plate 81 or the auxiliary driving dog 64 of an overtaken carrier.

The stop plate 81 forms part of a stop assembly shown in FIGS. 2 and 3. This assembly includes a mounting plate 82 suitably secured to the power track 10. A base plate 83, having an upper portion 84 and a portion 85 providing a vertically offset platform 86, is adjustably secured to the mounting plate 82 by a pair of upstanding screws 87 (only one of which is shown), each carrying a pair of nuts 88. A pivot shaft 89 is supported between a pair of blocks 90 attached to the upper portion 84 of the base plate 83. The stop plate 81 is formed by the lower flange of a C shaped arm 91, having an upper portion 92 which is weldedto a sleeve 93 on the shaft 89. The arm 91 can thus be rocked on the shaft by a suitable actuator such as the solenoid 94 mounted on the offset platform 86 of the base plate and connected to the arm 91 by a lever 95. A bumper 96 mounted on the upper portion 84 of the base plate 83 limits outward or releasing movement of the arm 91, as indicated by the broken line position of the arm 91 in FIG. 2. Also, a bumper 97 secured to the side of the arm 91 .adjacent the power track 10 defines the operative or carrier stopping position of the arm 91 and its stop plate 81. As shown in FIG. 3, this stopping position is one in which the stop plate 81 extends into the path of travel of only a laterally projecting portion of the holdback dog 59 of a carrier, and does not extend across the path of carrier travel an amount sufficient for positive engagement by the retaining cam portion 63 of a carrier; in fact, such positive engagement is prevented by the plowshaped forward portion 66 on the retaining cam.

The stop assembly also includes an antibackup member 98 on the lower end of an arm 99 connected to a second sleeve mounted on the pivot shaft 89 for free rocking movement, and gravity biased to the position shown in FIG. 3 in which the member 98 overlaps the driving dog 58 of the carrier.

The stop assembly is mounted with the axis of the pivot shaft 89 extending at an acute angle to the longitudinal center line of the tracks, and the stop arm 91 is secured to the sleeve 93 so that the vertical portion of the arm 9] extends parallel to the side of the power track 10. As a result of this angular relation of the parts, movement of the arm 91 from carrier stopping to released position includes a forward component of motion of the stop plate 81 for ease of disengagement from the holdback dog 59 of a carrier. This angulation is not employed in mounting the antibackup am 99.

When a carrier, being propelled by a pusher unit at normal track spacing as shown in FIG. 1, approaches a stop plate 81 which is in stopping position, contact first occurs between the leading edge of the stop plate and the holdback portion 36 of the pusher member 24 causing the pusher member to pivot to a position of disengagement from the carrier driving dog 58, and to be retained in this position by the upper surface of the stop plate as the holdback dog 59 of the carrier abuts against the leading edge of the stop 81 and the antibackup member 98 which had been pushed aside, swings back into overlapping relation with the carrier driving dog 58 to limit rebounding carrier movement.

With the carrier stopped, a pusher member 24 propelling a following carrier overtaking the stopped carrier, as indicated by the front carrier trolley 44A shown in broken line at the left of FIG. 1, is moved to disengaged position by the auxiliary driving dog 64 on the rear trolley 45 and is held in this position while passing over the retaining cam 63 of the stopped carrier. This action is similar to that illustrated in FIG. 7 for the pusher member 71. The following carrier is stopped by engagement of its holdback dog 59 with the auxiliary driving dog 64 of the leading carrier, this engagement being insured by the beveled surface 65 on the leading carrier and the guide surface 60 on the following carrier.

The transfer of a carrier under power from a forwarding to a receiving power line is accomplished by decreasing the spacing between the power track of the forwarding power line and the carrier track as illustrated in FIG. 5. At this reduced spacing'indicated by the dimension 102, the auxiliary pusher 28 formed by the nose of the puser bracket 23 (or the auxiliary pusher 78 on the pusher member 71 of FIG. 6 and 7) is engageable with the auxiliary driving dog 64 of a carrier to advance the carrier into a position where the main driving dog can be-picked up by a pusher unit on the receiving power line.

Positive propulsion of a carrier, which is preferred for traversing vertical curves of a system, is also obtained by reducing the spacing between the power track 10 and carrier track as shown in FIG. 4. This reduced spacing, indicated by the dimension 104, causes a pusher member, when engaged with the main carrier driving dog 58, to be displaced thereby to almost the limit of retracting movement, defined by abutment between the bracket tongue 27 and the pusher member web 31. In this retracted position of the pusher, the main driving face 34 thereof has increased overlapping engagement with the carrier driving dog 58; also, the holdback face 35 of the pusher member has increased engagement, overlapping the secondary holdback dog 61 of the carrier and thereby decreasing the amount of relative movement which can take place between the carrier and a pusher unit longitudinally of the path of travel.

Iclaim:

1. In a conveyor of the type having a carrier track, a power track mounted in spaced relation with the carrier track, a carrier on the carrier track provided with a driving dog engageable by a pusher unit of a propelling member supported on the power track for imparting forwarding movement to the carrier; the improvement wherein:

the pusher unit includes a main driving face and an auxiliary driving face, the main driving face and a cammingportion being formed on a pusher member;

means mounting the pusher member for movement between an engaged and a disengaged position of the main driving face relative to a carrier driving dog at a normal spacing between the carrier and power tracks in response to contact of the camming portion with an object in the path of pusher travel;

and an auxiliary driving dog on the carrier, said auxiliary driving dog being engageable by said camming portion of the pusher member at said normal spacing and by said auxiliary driving face of the pusher unit at a spacing between the carrier and power tracks which is less than said normal spacing.

2. A conveyor according to claim I wherein the carrier is provided with a pusher member retaining cam adapted to hold the pusher member in said disengaged position in response to contact between the pusher member camming portion and said retaining cam at said normal track spacing, and wherein said retaining cam is formed with said auxiliary carrier driving dog.

3. A conveyor according to claim 2 wherein the carrier includes a main holdback dog adapted to be abuttingly engaged by the auxiliary driving dog of an immediately preceding overtaken carrier.

4. A conveyor according to claim 3 wherein the carrier includes a guide surface adapted to be overlapped by the retaining cam of a preceding overtaken carrier.

5. A conveyor according to claim 1 wherein said pusher unit includes a pusher bracket, structurally united with the propelling member;

means connecting the pusher member to the pusher bracket for limited pivotal movement between a retracted and an extended position relative to the propelling member. the pusher member being biased to the extended position;

and the pusher member extending rearwardly from the pivot means with respect to the direction of forwarding carrier movement and having said main driving face and a holdback face, said driving and holdback faces being spaced longitudinally of the pusher membenand wherein said auxiliary driving face of the pusher unit is located forwardly of the main driving face.

6. A conveyor according to claim 5 wherein said auxiliary driving face is formed by a portion of the pusher bracket projecting forwardly of the pivot means.

7. A conveyor according to claim 5 wherein said auxiliary driving face is formed at least in part on a portion of the pusher member projecting forwardly of said pivot means.

8. A conveyor according to claim 5 wherein the holdback face on the pusher member in the retracted position thercof extends closer to the carrier track than said main driving face.

9. A conveyor according to claim 8 wherein the carrier includes a main holdback dog and a secondary holdback dog located forwardly thereof and projecting a lesser distance toward the power tracks, said secondary holdback dog being engageable with the holdback face of the pusher member at a spacing between the carrier and power tracks less than said normal spacing.

10. A conveyor according to claim 1 wherein the pusher unit includes a pusher bracket structurally united with the propelling member and carrying pivot means to which the pusher member is connected, and stop means on the pusher member and bracket limiting movement of the pusher member in directions toward and away from the propelling member.

11. A conveyor according to claim 10 wherein the pusher bracket includes a portion projecting forwardly of said pivot means, said auxiliary driving face of the pusher unit being fonned on said forwardly projecting bracket portion.

12. A conveyor according to claim 1 wherein the carrier includes a main holdback dog having a portion which extends transversely of the path of travel a distance greater than does the auxiliary driving dog, a stop plate mounted adjacent the carrier track at a location where the carrier and power tracks are arranged at said normal spacing for movement to andfrom a stopping position, the stop plate in stopping position being abuttingly engageable only by said transversely extending portion of the main holdback dog, and a lateral extension on the camming portion of the pusher member engageable with the stop plate in the stopping position thereof.

13. A conveyor according to claim 12 wherein the auxiliary driving dog is combined with a pusher-retaining cam, the pusher-retaining cam having means at the forward end thereof for imparting movement to the stop plate away from the stopping position in the event of engagement therewith.

14. In a power and free conveyor having a carrier track, a power track arranged in spaced relation therewith and supporting a propelling member, an improved pusher unit mounted on the propelling member for imparting forwarding movement to a carrier on the carrier track comprising:

a bracket member adapted to be secured to the propelling member;

a pusher member having a main driving face, a holdback face and a camming portion in advance of the holdback face;

means connecting the pusher member to the bracket member for limited pivotal movement between a retracted and an extended position relative to the propelling member, the pusher member projecting rearwardly from the pivotal axis of the connecting means with reference to the direction of forwarding movement and said camming portion assuming an acute angle to the longitudinal center line of the propelling member when the pusher member is in said extended position;

and an auxiliary driving face on one of the puser and bracket members. the auxiliary driving face being located forwardly of the main driving face and at a lesser distance from the propelling member than the main driving face when the pusher member is in said extended position.

15. An improved pusher unit as set forth in claim 14 wherein said auxiliary driving face is formed on a portion of the bracket member which projects forwardly of the pusher member.

16. An improved pusher unit as set forth in claim 14 wherein the holdback face of the pusher member projects from the propelling member a distance greater than the main driving face when the pusher member is in said retracted posi' tion.

17. In a power and free conveyor having a carrier track. a power track arranged in spaced relation therewith and supporting a propelling member equipped with pushers each movable between extended and retracted positions relative to the propelling member in response to contact with an object in the path of pusher travel. an improved construction for controlling movement ofa carrier on the carrier track comprising main driving and holdback dogs rigidly mounted at the front of the carrier and projecting toward the power track. a secondary holdback dog forwardly of and projecting a lesser distance toward the power track than the main holdback dog. each pusher having driving and holdback faces which overlap the main driving and holdback dogs of the carrier at a normal spacing between the carrier and power tracks and which overlap the main driving and secondary holdback dogs of the carrier with decreased longitudinal clearance at a spacing between the carrier and power tracks less than said normal spacing.

18. A power and free conveyor according to claim 17 wherein a portion of the carrier intermediate the driving and holdback dogs supports a pusher in a retracted position at said lesser track spacing, and means limiting further retracting movement of said pusher to an amount less than said overlap.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,559,585 Dated February 2, 1971 Inventor) George D. Lempio PAGE 1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 5t 5, change "line," to --link-- Column 7, line 1, change "puser" to -pusher--. column 3 aft line 18,

insert the following claims 19-23, inclusive:

19. In a conveyor of the type having a carrier track, a power track mounted in spaced relation with the carrier track, a carrier on the carrier track' provided with a main driving dog, and pusher means on a propelling member supported on the power track for imparting forwarding movement to the carrier; the improvement wherein the pusher means includes a pusher member having a main driving face, a holdback face, and a camming portion located in advance of the main driving face;

means mounting the pusher member on the propelling member f or movement in directions toward and away from the propelling member between a retracted and an extended position relative thereto;

stop means'limiting movement of the pusher member in each of said 3 directions, the pusher member being biased to the extended position and movable between an engaged and a disengaged relation of the main driving face with a carrier main driving dog at a normal spacing between the carrier and power tracks in-response to contact of the camming portion with an object in UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3 ,559 58S Dated February 2 1971 George D. Lempio PAGE 2 Inventor(s) It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:

the carrier including a main holdback dog projecting toward the t track, the carrier main driving and holdback dogs at the normal spacing tween the carrier and power tracks being overlapped by the driving and back faces of the pusher member to an extent less than the available mo ment of the pusher member to said retracted position;

i i and a reduced spacing between the'carrier and power tracks, the

i ier main driving and holdback dogs at said reduced spacing being overla by the driving and holdback faces of the pusher member to an extent grc than the available movement of the pusher member to said retracted pos whereby movement of the carrier is positively controlled by the pusher her at said reduced spacing.

20. A conveyor according to claim 19 wherein of the 0:

intermediate said driving and holdback dogs engages and moves the push ward the power track at said reduced track spacing.

21. A conveyor according to claim 19 wherein the pusher means cludes a pusher bracket structurally united with the propelling member carrying pivot means to which the pusher member is connected.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,559,585 Dated February 1971 Inventor) George D. Lempio P 3 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

A conveyor according to claim 21 wherein the stop means lin movement of the pusher member is provided on the pusher member and p bracket.

23. A conveyor according to claim 19 wherein an auxiliary drivin and a pusher member retaining cam are mounted on the carrier in trailir lation to said main driving dog, said auxiliary driving dog and pusher me retaining cam being engageable by said camming portion of the pusher m her to prevent engagement between said auxiliary driving dog and said m:

driving face of the pusher member at said normal spacing between the ca and power tracks; and an auxiliary pusher carried by the propelling mem said main and auxiliary driving dogs being non-engageable by the auxiliar pusher at said normal track spacing and said auxiliary driving dog being able by said auxiliary pusher at a reduced track spacing.

nnPA an nu .....-.-r... a- Inn UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 559 585 Dated February 2 a 1971 Inventor(s) George D. Lempio PAGE 4 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the cover sheet [54] "18 Claims" should read 23 C Signed and sealed this 11th day of May 1971.

(SEAL) Attest:

EDWARD M FLETCHER,JR. WILLIAM E SCHUYLER Attesting Officer Commissioner of Pate 

1. In a conveyor of the type having a carrier track, a power track mounted in spaced relation with the carrier track, a carrier on the carrier track provided with a driving dog engageable by a pusher unit of a propelling member supported on the power track for imparting forwarding movement to the carrier; the improvement wherein: the pusher unit includes a main driving face and an auxiliary driving face, the main driving face and a camming portion being formed on a pusher member; means mounting the pusher member for movement between an engaged and a disengaged position of the main driving face relative to a carrier driving dog at a normal spacing between the carrier and power tracks in response to contact of the camming portion with an object in the path of pusher travel; and an auxiliary driving dog on the carrier, said auxiliary driving dog being engageable by said camming portion of the pusher member at said normal spacing and by said auxiliary driving face of the pusher unit at a spacing between the carrier and power tracks which is less than said normal spacing.
 2. A conveyor according to claim 1 wherein the carrier is provided with a pusher member retaining cam adapted to hold the pusher member in said disengaged position in response to contact between the pusher member camming portion and said retaining cam at said normal track spacing, and wherein said retaining cam is formed with said auxiliary carrier driving dog.
 3. A conveyor according to claim 2 wherein the carrier includes a main holdback dog adapted to be abuttingly engaged by the auxiliary driving dog of an immediately preceding overtaken carrier.
 4. A conveyor according to claim 3 wherein the carrier includes a guide surface adapted to be overlapped by the retaining cam of a preceding overtaken carrier.
 5. A conveyor according to claim 1 wherein said pusher unit includes a pusher bracket, structurally united with the propelling member; means connecting the pusher member to the pusher bracket for limited pivotal movement between a retracted and an extended position relative to the propelling member, the pusher member being biased to the extended position; and the pusher member extending rearwardly from the pivot means with respect to the direction of forwarding carrier movement and having said main driving face and a holdback face, said driving and holdback faces being spaced longitudinally of the pusher member, and wherein said auxiliary driving face of the pusher unit is located forwardly of the main driving face.
 6. A conveyor according to claim 5 wherein said auxiliary driving face is formed by a portion of the pusher bracket projecting forwardly of the pivot means.
 7. A conveyor according to claim 5 wherein said auxiliary driving face is formed at least in part on a portion of the pusher member projecting forwardly of said pivot means.
 8. A conveyor according to claim 5 wherein the holdback face on the pusher member in the retracted position thereof extends closer to the carrier track than said main driving face.
 9. A conveyor according to claim 8 wherein the carrier includes a main holdback dog and a secondary holdback dog located forwardly thereof and projecting a lesser distance toward the power tracks, said secondary holdback dog being engageable with the holdback face of the pusher member at a spacing between the carrier and power tracks less than said normal spacing.
 10. A conveyor according to claim 1 wherein the pusher unit includes a pusher bracket structurally united with the propelling member and carrying pivot means to which the pusher member is connected, and stop means on the pusher member and bracket limiting movement of the pusher member in directions toward and away from the propelling member.
 11. A conveyor according to claim 10 wherein the pusher bracket includes a portion projecting forwardly of said pivot means, said auxiliary driving face of the pusher unit being formed on said forwardly projecting bracket portIon.
 12. A conveyor according to claim 1 wherein the carrier includes a main holdback dog having a portion which extends transversely of the path of travel a distance greater than does the auxiliary driving dog, a stop plate mounted adjacent the carrier track at a location where the carrier and power tracks are arranged at said normal spacing for movement to and from a stopping position, the stop plate in stopping position being abuttingly engageable only by said transversely extending portion of the main holdback dog, and a lateral extension on the camming portion of the pusher member engageable with the stop plate in the stopping position thereof.
 13. A conveyor according to claim 12 wherein the auxiliary driving dog is combined with a pusher-retaining cam, the pusher-retaining cam having means at the forward end thereof for imparting movement to the stop plate away from the stopping position in the event of engagement therewith.
 14. In a power and free conveyor having a carrier track, a power track arranged in spaced relation therewith and supporting a propelling member, an improved pusher unit mounted on the propelling member for imparting forwarding movement to a carrier on the carrier track comprising: a bracket member adapted to be secured to the propelling member; a pusher member having a main driving face, a holdback face and a camming portion in advance of the holdback face; means connecting the pusher member to the bracket member for limited pivotal movement between a retracted and an extended position relative to the propelling member, the pusher member projecting rearwardly from the pivotal axis of the connecting means with reference to the direction of forwarding movement and said camming portion assuming an acute angle to the longitudinal center line of the propelling member when the pusher member is in said extended position; and an auxiliary driving face on one of the puser and bracket members, the auxiliary driving face being located forwardly of the main driving face and at a lesser distance from the propelling member than the main driving face when the pusher member is in said extended position.
 15. An improved pusher unit as set forth in claim 14 wherein said auxiliary driving face is formed on a portion of the bracket member which projects forwardly of the pusher member.
 16. An improved pusher unit as set forth in claim 14 wherein the holdback face of the pusher member projects from the propelling member a distance greater than the main driving face when the pusher member is in said retracted position.
 17. In a power and free conveyor having a carrier track, a power track arranged in spaced relation therewith and supporting a propelling member equipped with pushers each movable between extended and retracted positions relative to the propelling member in response to contact with an object in the path of pusher travel, an improved construction for controlling movement of a carrier on the carrier track comprising main driving and holdback dogs rigidly mounted at the front of the carrier and projecting toward the power track, a secondary holdback dog forwardly of and projecting a lesser distance toward the power track than the main holdback dog, each pusher having driving and holdback faces which overlap the main driving and holdback dogs of the carrier at a normal spacing between the carrier and power tracks and which overlap the main driving and secondary holdback dogs of the carrier with decreased longitudinal clearance at a spacing between the carrier and power tracks less than said normal spacing.
 18. A power and free conveyor according to claim 17 wherein a portion of the carrier intermediate the driving and holdback dogs supports a pusher in a retracted position at said lesser track spacing, and means limiting further retracting movement of said pusher to an amount less than said overlap. 